It seems like every day a new study indicts a commonly used chemical called bisphenol A (BPA). It was only a few weeks ago that I wrote an article entitled “Is That Drink Container Making Your Children Obese?” which pointed out the links between BPA found in soda cans and obesity in children. Today, a new study adds to the mounting evidence against the use of this chemical. Researchers at the University of California – Berkeley have linked BPA to thyroid effects on pregnant women and newborn boys. The study is published in the journal Environmental Health Perspectives.

A receipt printed on thermal paper. As a demonstration of principle, a heat source (in this case, a lighter) is held near the paper, so it darkens. (credit: IIVQ – Tijmen Stam via Wikimedia Commons)

BPA is an estrogen-like chemical that used in the creation of many plastics, can liners, and sales receipts from thermal printers. Pictured above, you can see how the receipt paper changes color when exposed to a heat source. To be honest, BPA is so common that it shows up in urinary samples of almost everyone in U.S. Recently, the U.S. Food and Drug Administration banned the use of BPA in baby bottles and sippy cups. Pressure continues to mount from many in the research community to get BPA removed from all food related items.

In the Berkeley study, urine samples of 335 pregnant mothers were checked for BPA levels, as well as blood sample from the mothers and the newborns shortly after birth to test for thyroid levels. For every doubling of the levels of BPA in the mother’s urine samples, a decrease in total thyroxine, a thyroid secretion used to regulate cell metabolism in the body, was also seen. This decrease is essentially considered a hypothyroid condition. For newborn boys, each doubling of BPA levels linked to a 9.9 percent decrease in thyroid stimulating hormone (TSH), which indicates a hyperthyroid effect.

According to the Berkeley press release, study lead author Jonathan Chevrier, research epidemiologist at UC Berkeley’s Center for Environmental Research and Children’s Health (CERCH) said, “Most of the women and newborns in our study had thyroid hormone levels within a normal range, but when we consider the impact of these results at a population level, we get concerned about a shift in the distribution that would affect those on the borderline…In addition, studies suggest that small changes in thyroid level, even if they’re within normal limits, may still have a cognitive effect.”

Though the FDA has yet to outright ban the use of BPA in products, studies like this suggest it may be advisable for pregnant women to avoid BPA as much as they can. Soda cans are considered the most significant source of BPA in the American diet. Avoiding receipts printed from thermal printers is another big source. Also, in plastics, look for the recycling symbol with the number 7 which denotes BPA in the product.